Mineral weathering and ectomycorrhizae of Picea glauca x engelmannii (Moench.) Voss with emphasis on Piloderma

Piloderma is one of the most recognizable ectomycorrhizal fungi in many forest ecosystems in North America. It is a broad host range fungus commonly observed in many economically important coniferous and deciduous trees in central interior British Columbia. Piloderma may benefit these forests through increased soil mineral weathering and nutrient availability. This thesis investigates the role of Piloderma in the weathering of common soil minerals to supply K and/or Mg in the rhizosphere soils of Picea glauca. I also documented the changes in the physical, chemical and mineralogical properties of rhizosphere soils influenced by Pilodermaand other common ectomycorrhizal fungi. In the first study, I investigated the role of Piloderma in weathering and extracting K and/or Mg from biotite, microcline, and chlorite. Specifically, I compared the in vitro growth, morphology, and chemical properties of Piloderma growing within three K and/or Mg-containing minerals that are commonly found in soils of central interior British Columbia. Piloderma cultures were grown for 110 days in medium enriched with K and/or Mg from biotite, microcline, and chlorite, in K and Mg poor media and in medium optimized for proper fungal growth. Chemical analysis indicated that Piloderma more efficiently weathered biotite to obtain K over microcline. The different growth, morphologies, and small amounts ofMg found in all treatments indicated that chlorite and biotite provide a sufficient supply ofMg. Piloderma grown in treatments with insufficient K showed distinct fibrillar growths, hypha! swellings, and hyphae devoid of ornamentation and could be indicative of nutrient deficiency. This study indicated that considerable amounts of K and minor amounts of Mg are essential for !"roper Piloderma growth and, perhaps more that Piloderma could provide sufficient amounts of K from the weathering of biotite. In the second study, the pH, total C and N, cation exchange capacity, and the contents of mica, chlorite, kaolinite, 2:1 type expandable clays, and amorphous materials were compared between two ectomycorrhizosphere soils (soils containing considerable ectomycorrhizal colonization) and non-ectomycorrhizosphere soils (bulk) of Picea glauca x engelmannii (Moench.) Voss) to elucidate the role of ectomycorrhizae on the chemical and mineralogical properties of soils in the field. The two ectomycorrhizosphere soils were characterized by colonization dominated by (1) Piloderma, and (2) Inocybe lacera-like and ~ Hebeloma-like morphotypes or where Piloderma colonization was <1 %. Results showed that pH was one unit lower in ectomycorrhizosphere compared to nonectomycorrhizosphere soils. Total C and N were significantly higher in ectomycorrhizosphere soils where C was three times higher and N was two times higher than non-ectomycorrhizosphere soils. Cation exchange capacity as well as exchangeable K+, and Na+ were higher in ectomycorrhizosphere soils compared to bulk soils where K+ >Na+. Base saturation was significantly lower in non-ectomycorrhizal soils compared to both ectomycorrhizosphere soils. Compared to bulk soils X-ray diffraction did suggest the transformation of mica and chlorite to 2:1 type expandable clays in ectomycorrhizosphere soils.